Devices for introducing gases into liquids serve to admix the liquids with certain gases so as to initiate or aid biological and/or chemical processes in the liquids under participation of the gases introduced. Thus, the introduction of gases such as, e.g., oxygen or air, may serve to supply these gases to microorganisms present in the gas-treated liquid. The introduction of gases into a liquid may, however, also have the effect that substances present in the liquid change over into the gaseous phase and flow off; this occurs when blowing out carbonic acid or ammonia, e.g. The introduction of gases into liquids has various effects which, depending of the respective individual case, may be judged as advantageous or as disadvantageous. Thus, e.g., the motion of a liquid associated with the introduction of gases into the respective liquid, which motion is caused by the movement of the gas bubbles in the liquid, may be considered advantageous in some instances, because such a motion of the liquid counteracts the formation of deposits in the respective container or basin in which gases are introduced into the liquid. Frequently, it is also the aim to incorporate in a liquid as large a percentage of the gases introduced as possible; this is favorably influenced by as small a size of the gas bubbles introduced into the respective liquid as possible. An introduction of gases into liquids in the form of fine bubbles can be attained if the gases to be introduced are fed into the liquid through a porous foil submerged beneath the surface of the liquid into which the gases are to be introduced. This is particularly provided for biological sewage treatment plants, to introduce oxygen from air into the activated sludge mixture present in a treatment basin. Devices have been known with large-area gas distributors, and such a large-area configuration of the gas distributors leads to increased structural expenditures due to the provision of measures for supporting the porous foil against the internal pressure prevailing in the chambers of the gas distributors and required for the introduction of gas into the liquid, and if there are larger distances between individual, large-area gas distributors, there also occurs an non-uniform distribution of the introduction of the gas into the liquid, and from the non-uniform introduction of gas there also result currents within the liquid. Such currents may reduce the dwell time of the gas bubbles in the liquid, and, correspondingly, a smaller percentage of the gases introduced into the liquid is accommodated by the liquid. The above-mentioned wider distances between the individual gas distributors mostly result from the economically-based desire to get by with as small a total area of gas distributors as possible.
In a known device of the initially defined type, the gas distributors are designed in the form of a flat air hose consisting of an elastic material, in particular rubber, which is provided with a plurality of air outlet openings at its upper wall, one end of this hose being connected to an air supply duct, cantilevering from this connection site, rod-shaped carrying elements being slid into this hose, the carrying elements also cantilevering from this connection site at the air supply duct. This construction is structurally complex and, due to the design of the gas distributors and the cantilevering structure of the same, it is restricted to a relatively short longitudinal extension of the gas distributors, so that also in this instance, for economical reasons and so as not to make an access to the basin difficult due to a great number of air supply ducts, care must be taken to get by with a small overall area of gas distributors and to put up with greater distances between the air supply ducts, which, however, as mentioned before, will lead to a non-uniform distribution of the gas introduction into the liquid and the disadvantages entrained thereby.